DIDO

I breastfed my first DS till he self weaned at 20 months, I believe because I was pregnant with #2. I will be happy to continue breastfeeding Glenn untill he is ready to wean on is own as well.

Katanya, you have covered pretty much all of the reason i would have listed as well. People get a bit funny about breastfeeding an older child and think its just "wrong" or not "normal" but the world average for weaning is between the ages of 5 and 7!!!! so really its those who wean early that are the not the norm.
When I first started breastfeeding I didn't really know how long I would breastfeed for or how long your suppose to and was just going to breastfeed for as long as the age group you could buy formula for. I figured if they still need formula at 1 then I would breastfeed and if the still get toddler formula as toddlers then i would breastfeed. If there is benifits in giving formula to the older toddler then there is even more so in breastmilk.